We are studying the effects of treatment with narcotics on behaviors elicited by dopaminergic agonists and on various measures of dopamine function in the CNS of rats. We are attempting to determine the mechanism by which narcotics interact with dopamine systems, by the combined use of behavioral measures of sterotypy and locomotion, dopamine receptor binding assays as indicators of postsynaptic changes, and HPLC determinations of levels of dopamine and metabolites in caudate and mesolimbic areas as indicators of presynaptic events.